All politics is local, said Tip O’ Neill, the former Democratic Speaker of the House from Massachusetts. For years the adage shaped the tactics of campaigns, nudging candidates to tailor their rhetoric and platforms to the specific concerns of the constituents they hoped to represent. But it is no longer true, as writers like Matt Bai have observed. “Politics in the online age is increasingly borderless and can often be shaped more by national causes than by anything having to do with local constituents,” Bai wrote in the fall of 2010, as he observed Christine O’Donnell, a weak candidate with no discernible organization, surf a wave of anger at the status quo to a primary win. The nationalization of our politics was one of the major stories of the 2010 midterms, when political experience became a liability and races boiled down to which candidate could claim the outsider’s mantle. So it is again this year.

Though fought in a collection of states, each with its own parochial concerns, the Republican primary has been marked by national surges and swoons. With the exception of Mitt Romney, whose level of support has stayed relatively steady, the fortunes of the Republican candidates have swung dramatically. Over the past two months, there have been five lead changes in the national polls. These swings have been triggered by two types of events: nationally televised debates and wins in state contests. Heading into South Carolina, Newt Gingrich was a broken candidate who hadn’t finished higher than fourth and lagged badly in the national polls. His win in the Palmetto State nudged voters nationwide to climb aboard his bandwagon. After Gingrich was pummeled in Florida, his support collapsed across the country.

The upshot of a nationalized contest is that no state is safe. Michigan should be a cakewalk for Romney, a native son whose father was a venerated auto-company executive and popular governor. Romney won the state by nine points in 2008. He has a superior war chest and the support of local party bigwigs. Since June, he has visited Michigan 11 times. Rick Santorum has been to the state exactly once: Feb. 16, on the heels of a flurry of polls that showed him surging to an improbable lead.

To local analysts, the specter of Romney’s losing Michigan is unthinkable. “There isn’t any reason in the world Rick Santorum should be a factor in Michigan at all. He’s never been here. He has no connection to the state. He’s only seemingly doing well because he’s viewed as the latest anti-Romney in the party,” says Bill Ballenger, a former Republican lawmaker and Michigan political analyst. “But the nature of American politics has changed so radically. It’s become so nationalized and media-driven. You can do everything a campaign should be doing — and believe me, Romney has done that, while Santorum and [Ron] Paul and Gingrich have not — but if the narrative out there is ‘Anybody but Romney,’ even with Romney’s ties to the state, it may be difficult for him to overcome.”

The battle in Michigan has been revealing not just for what it says about Romney’s struggles to connect with Republican voters but also for the way in which he and Santorum are looking beyond their immediate audience to drive a national message. Last week, Romney doubled down on his opposition to the Obama Administration’s auto bailout by writing an editorial in the Detroit News that slammed the initiative as “crony capitalism on a grand scale” to benefit “Obama’s union allies.” Not to be outdone, Santorum used a speech at the Detroit Economic Club on Thursday to note that he too was against the auto bailout. Both candidates belabored the point in the face of the fact that in Michigan, labor is a dominant force, and the bailout remains popular. Both Chrysler and GM are resurgent. GM recorded its most profitable year in history in 2011, netting $7.6 billion.

The nationalization of presidential politics doesn’t mean that local and regional demographics don’t matter. Romney has been strong in less-conservative states. Santorum has done well in the Midwest, where he frames himself as the grandson of a coal miner who understands the economic pain afflicting the region. Gingrich’s lone win was in the Deep South, where he hopes to resurrect his flagging campaign on March 6, Super Tuesday. “If any of the three loses our home state … you have, I think, very, very badly weakened candidacies,” the Georgian said on Sunday. “I was home campaigning for the last two days precisely to say to all of my friends back home, Georgia really matters. You cannot take this for granted.”

Romney too is desperate to avoid an ignominious defeat in his home state. “That won’t happen,” he said last week. Maybe not. But the fact that it could — and his strategy for sidestepping that embarrassment — says a lot about how politics is no longer a local affair.